Voice Is Data: Tech Won't Be Able To Stop VoIP In The Air

from the of-course-not dept

With increasing attempts to turn internet access on in the sky, there's been some concern about people making VoIP calls from airplanes, just as there is a concern over mobile phone use in the sky being too "annoying." Some of the companies providing internet-in-the-sky have claimed that they would block VoIP calls, but that's going to be pretty difficult. As we've pointed out in the past voice is just data and you can always find a way to disguise the data, such that it won't be blocked. And, indeed, that seems to be exactly what's happening. Andy Abramson talks about how he got around AirCell's VoIP blocking when talking to a friend who was on one of these wired airplanes. There's always going to be away around those things, so unless Congress really decides to ban all voice calls on phones, why not wait and see if people chatting really is a problem?

VoIP is tricky to the non experienced. Most VOIP systems use a SIP based interface, which employs UDP and frequently has troubles- a wide range (Over 100, if I remember correctly) of ports have to be opened and forwarded to even enable something more than one-way audio. VoIP also needs a link with very low (sub 200ms) latency to the switch. Most satellite-based systems (Which I have no clue what AirCell uses, but the previous ConneXion service was satellite based) had latency upwards 400ms.

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Mythbusters experiments are hardly scientific.

Personally, I have a problem when someone takes the word of ex Hollywood Prop guys over the R&D established by an entire industry.

Understand that your consuming entertainment with a budget of $10,000, not real-life research. Many navigational systems cost upwards $250,000 so think about if a show with a $7,000 budget can afford to really perform a true-to-life scientifically controlled experiment.

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There are numerous reports in the Aviation Safety Reporting System (ASRS) database of navigation errors which ceased after the crew asked for PEDs to be turned off. Although the VOR system was most often cited, the instrument landing system (ILS) was reported to have been affected 17 times, radar altimeters 10 times, autopilot systems eight times, ground-proximity warning systems seven times and an engine fuel controller once, in data through March 2001. Significantly, in a number of cases, the cockpit crew verified that the PED was the source of the error by having it turned back on and seeing the navigation error repeat, before requiring that the device be secured.

Personal electronics have caused avionics interference on airliners and general aviation aircraft. These devices are being used on revenue flights, including cell phones during approach. Passengers are not aware that their electronics are restricted for safety reasons.

Try it sometime - doesn't work above about 5,000 feet - ever. I know, out of curiosity and need for data connections I've tried AT&T and Verizon many times - no dice.

"If it was a problem, they wouldn't have the $2/min air phones in every aisle."

As a very frequent flyer, I can tell you phone calls en route will be highly annoying to me at least. You're seeing more and more "cell free" areas in public places on the ground, why would cell usage when you're trapped shoulder to shoulder for hours on end be any less aggravating than in a restaurant or movie?

Ever notice people use headphones on planes to listen to their iPod but don't hook up speakers? Why would listening to 1/2 of someone's phone call be any less rude than listening to music via speaker?

As for your $2/minute theory, I fly all the time and I can remember seeing someone using those phones perhaps once or twice over the past years. Reason? Too expensive. Even in first class, they are rarely used. Just because some company is foolish enough to pay to put them on planes doesn't mean they're a good business model. For example, there's very little competition to supply these in-flight phones. One or two smallish companies worldwide, and cerainly no major companies are vying for the business. Also, if there was any kind of volume of usage, you'd see prices drop to encourage even more use.

I tend to put credence in the Myhthbuster's test. If cell phones were truly dangerous electronically they would be banned altogether; any real physical risk is too risky. Airlines, aircraft manufacturers and the FAA eliminate other, even less likely sources of risk; surely they wouldn't stop at a total ban on turning on cell phones if they were truly a flight risk.

I also reject the $2/min competition as the reason for the ban, obviously.

Then, why are cell phones banned? My theory: Flight crews don't want to have to deal with passengers refusing to get off calls, and with other passengers complaining about people making noisy, angry or otherwise uncomfortable-for-your-neighbor calls.

The $2/min option gives the "must-calls" a way to satisfy that need with very little likelihood they will stay on and chat for long vs. cell phones where the flat fee plans guarantee that the more mindless and rude you seem to be, the longer you're going to yammer on.

Just add jitter

To back up Steve's comment (#7), the way to stop VOIP from being workable is to add jitter to the packet transmission times. This doesn't affect TCP traffic which can handle transmission delays, but the time-sensitive data of a VOIP session gets really screwed up by it. You could even design the aircraft to ground link to rely on this, say by using Time Delay Multiplexing between aircraft, and now the network link is naturally hostile to voice traffic.

it seems to me, and call me wacky, but if an airplane is so sensitive that the MINISCULE transmissions of a cell/pda can cause it to freak out, what the EFF are we doing putting our bodies in these things

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To comment #11. I followed the link. It's a news article in Aviation Week. It refers to some studies (unreferenced) and some recommendations, but does not offer any data that personal electronic equipment has ever caused any air travel accidents or even near-misses.

And let's not forget that NASA has had serious lapses in judgment that led to tragic events with lives lost.

My friend's dad is an engineer at Boeing...

...and was specifically tasked with finding this out. There is no problem whatsoever with any plane newer than a DC9. It's more of a problem (with the newer planes) to the cell towers on the ground than it is to the plane itself.

Of course, the biggest problem is sitting next to someone. I was getting my hair cut the other day at Supercuts and there was this guy (who seemed to be gay) waiting talking about all his dates with some girl. TMI.

The true intent

I know this will shock and dismay but I'm
supporting the VOIP is data side of this.
While I loath the thought of some jackass
yakking on the phone in the steat next to
me while I'm trying to sleep- data is data.

If it's OK to connect to the internet then
it shouldn't matter what is in the packets
being tossed too and fro.

This reveals the true intent of the regulations,
which is to extract every possible smidgen of
income from the captives during their stay in
purgatory.

Cellular Networks Are Terrestrial

Poster #15 is onto the real reason you can't use a cellphone in the air: cellular networks are NOT designed for this, and it screws them up.

That's why the FCC has a ban on airplane cell use, and the FAA's ban is merely window dressing with "safety" as a justification. The people above who doubt the safety issue are right, given the evidence: how many phones do you think are forgotten and left on on any given flight? If planes are that vulnerable, I'd never get in one. What would that imply? A terrorist could crash a plane by using common cell phones, why bother looking for explosives at the security check?!! Why bother rushing the cockpit!? Just call 1-900-hijack at the coordinated time.

The reason cellphones at 30,000 feet are bad for cellular networks has to do with the network design, specifically two things endemic to cellular phone networks: 1) frequency re-use, and 2) tower handoff.

1) Cellular nets use frequency re-use to get more people onto their system using just the limited amount of spectrum they are leasing from the FCC. You can picture it this way: a guy in NYC uses Verizon Wireless (VZW) channel "1" to make a call. Obviously, a guy in Chicago, Denver, and San Francisco could also use VZW channel 1 to make a call at the same time without causing any interference to NYC. This is frequency re-use. Now extrapolate that to a much higher use level. Think of a guy in Manhattan using channel 1, another guy in the Bronx, and another guy in Brooklyn. Actually, think of the honeycomb-like cells in a beehive overlaid on the country, and then understand that so long as any two cells are non-contiguous, they may re-use the same channels. This concept is so important to cellular networks, that the networks are named after the concept. Any single user can drive around on the ground, moving from one cell to another, using channels, and never broadcasting so strongly that it interferes with someone else using the same channel a few miles away. Now imagine an airplane, overhead, and equidistant to 3 towers that are all re-using the same channels. If the airplane's phone signal could reach one tower, it would also reach the others, causing interference.

Note that the towers have antennae that are aimed along the surface of the earth, not into the sky. No cellular operator wants to waste energy transmitting to the sky! This further makes it difficult for airplanes to connect.

Commercial airplanes at cruise fly about 4-5 miles up. That's a long way. Then don't forget the tower antennas aren't aimed up there. Signal quality will be poor at best.

2) Now, for tower hand-off. Usually, when a person is talking on the cellphone while driving or on a fast train, the network is capable of understanding where the person is, which tower they are using, and how to transfer their call to the next tower along their route. Take the speed up to 500mph, and the network was never engineered to expect that, accommodate that, or make the hand-off. Now picture a situation where the network expects that this 500mph phone is on the ground, yet can't get a good idea of where it is, since it is visible to way more towers than normal. Which tower should it hand the call to? Yikes. Call drops.

Thus, cellular phones won't crash airplanes, but they will adversely affect the cellular network. They will at best provide spotty, poor, and short connections inside of airplanes, but usually nothing.

Remember the 9/11 phone calls from the hijacked airliners? This was a sad demonstration of how well cellphones work in the air. The planes were at lower altitudes, but still the calls were garbled, cut off, or not connected.

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I'm glad you understand the technical aspects and problems of radio communications, me after 30 years as a radio tech in aircraft I pretty sure WiFi in the sky (and cellphones when it happens) will casue aircraft incidents (if it hasn't happened already).
But of course you know better because they have $2/min air phones in every isle...... even though they operate differently and are statistacally short events.

As an aircraft avionics tech, I ain't flying in anything that allows Wifi or cell phones...

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Would you accept the word of an RF Engineer who's had over 35 years experience?

If so, take it from me, cell phones are not going to upset the avionics of the plane(s).

This whole bit of over caution was started because most devices used common IF strips as part of their receiving scheme. The theory was that at close proximity it would "mix down" the undesired signal thereby causing interference to the communications and guidance systems (HAH!).

When restrictions started appearing regarding various and sundry devices, many of us in the business allowed as to how if the equipment were that sensitive, wouldn't it make sense to shield it *and* the cables? This started a flurry of "nonsense-grams" involving those of us in the business, the FAA, the FCC and the Airplane Companies.

Since then, any interference from; cell phones, personal computers, walkie talkies, hand held video games and just about every other consumer device has been debunked.

The latest (and secret) fear on the part of the Government has been more a contribution of Homeland Security (you know, the folks who seem to want to spy/ strip search/ shoot first before determining facts). It is their fear that cell phones might be used as triggers for bombs.

Thus (because they don't want to tip their hands, those "sly devils") they're bringing up all those hoary old stories from the past. Never once did they seem to be able to expound on why it is that a bomb would get on the plane in the first place, and oh by the way shouldn't we sweat that one first?

What's really happening (Get a clue)

Doesn't the FAA have governing authority over airplanes and isn't it regulated completely separate from the FCC?

Shouldn't Aircell see themselves as a FAA-governed body?

It seems Aircell's management and VC firm (both very heavy on the Telco side) may be trying to play this out in the public opinion circuit and with longtime friend and chum Kevin Martin (FCC) instead of addressing the real issues with the FAA.

Sprint has been notorious for bringing products to market prematurely.